Sodium Selenite (Selenium)

A study in cats and dogs found no clear difference between sodium selenite and organic selenium.

Sodium selenite is a mineral salt used to add selenium to animal feeds. FDA regulates selenium additions to animal feeds under 21 CFR 573.920, which names sodium selenite and sodium selenate as allowed forms; the levels in that rule are set for livestock and poultry, not cats. Cats need selenium in small amounts, and complete foods add a measured dose. For a cat with a medical condition, ask your veterinarian before giving any selenium supplement.

Source: govinfo.gov

Sodium selenite is added to supply selenium, a trace mineral that works with vitamin E in antioxidant enzymes. Fish and meat contain selenium, but levels vary, so manufacturers add a small, measured amount to reach the target for cats. It is one of the most widely used selenium sources in pet food.

Selenium is part of glutathione peroxidase, an enzyme that protects cells from oxidative damage. It is also needed for thyroid hormone metabolism. Cats need only trace amounts. The Merck Veterinary Manual lists selenium among the trace minerals in small animal diets.

Source: merckvetmanual.com

Selenium in cat food comes from two places. Fish and meat carry natural selenium, and the amount depends partly on the soil and water where the animals or their feed came from. Manufacturers then add a measured amount, most often as sodium selenite, so the finished food reaches its target.

Pettings gives sodium selenite 3 out of 5 and lists it as a mineral. It appears on 140 of the 149 dry cat foods we list. Our How We Score page explains how ingredient scores are set. Each food's page shows how it scores overall.